Structures wherein axles are provided on bearings on automobile frames and wheels are supported on these axles are used in automobiles. Seal structures are provided on the bearings so as to prevent entry of foreign materials into the bearings such as mud and water splashed by the wheels.
FIG. 11 is a cross-sectional drawing for explaining the basic structure of a conventional bearing, wherein a bearing 100 includes an inner race 101, an outer race 102, rolling elements 103 that are provided between the inner race 101 and the outer race 102, and a retainer 104 for holding the rolling elements 103. Furthermore, the bearing 100 is provided with oil seals 105 so as to prevent incursion of foreign material from outside into the rolling elements 103.
An example wherein such a bearing 100 is applied to an automobile is shown in FIG. 12. As illustrated in FIG. 12, the outer race 102 is secured by a bolt 107 to an automobile frame 106, where the inner race 101 is attached to the outer race 102 with the rolling elements 103 interposed therebetween, where bolts 108 for holding the inner race 101 to the wheel are provided, and where a driveshaft 109 is connected to the inner race 101. The inner race 101 is rotated by the driveshaft 109, to rotate the wheel through the bolts 108. Oil seals 105 are provided between the inner race 101 and the outer race 102.
As illustrated in FIG. 13, the oil seal 105 is made from a slinger 111, which is L-shaped in cross-section, that fits into the inner race 101, a core 112, which is L-shaped in cross-section, that fits into the outer race 102, a seal member main unit 113 that is provided on the core 112, and ribs 114, 115, and 116 that extend from the seal member main unit to the slinger 111. The seal member main unit 113, including the ribs 114, 115, and 116, and the core 112 are stationary, along with the outer race 102, and do not rotate. On the other hand, the slinger 111 rotates together with the inner race 101.
Because the ribs 114, 115, and 116 contact the slinger 111, they maintain the seal performance. However, the sliding resistance produced through the contact of the ribs 114, 115, and 116 with the slinger 111 is large, consuming a portion of the motive force of the engine, and thus has a negative impact on fuel consumption. Moreover, the ribs 114, 115, and 116 undergo wear on surfaces during use, causing concerns regarding a reduction in seal performance if the amount of wear exceeds a given amount.
Given this, a seal structure that has reduced sliding resistance and that can maintain seal performance over an extended period of time is desired.